The invention concerns a method for lubricating rolls, especially work rolls of a rolling stand, and rolling stock passed between the rolls during the rolling operation, in which a lubricant-gas mixture, a lubricant-water-gas mixture, a lubricant-water mixture, and/or a grease-medium mixture is applied to the rolls or the rolling stock on the run-in side of the rolling stand.
The rolling stand comprises several mutually supporting rolls, including, for example, a work roll, which comes into direct contact with the rolling stock and in turn rolls on a generally larger backup roll or intermediate roll. Many hot rolling mills for rolling a metal strip have an integrated roll gap lubricating system. These systems are used for the purpose of improving the surface quality of the work roll and the strip and have become part of the standard equipment of a rolling mill on which high-quality strip is to be produced. In one widely used system, a mixture of water as the base medium with oil is applied to the rolling stock or to the work roll or backup roll.
In the cold rolling process, lubrication is customary. In this case, lubricant is applied to the rolling stock and/or to the work roll and/or is sprayed into the roll gap. The mixing of the oil and water is carried out far from the rolling stand. In most cases, an emulsion is used, which, in a complicated process in a circulation system, is separated, cleaned and resupplied to the lubricating system.
WO 03 002277 A1 discloses a method and a device for cooling and/or lubricating rolls, especially work rolls, of a rolling stand, in which water in the form of spray jets is used as a cooling medium, and oil, an oil-air mixture, an oil-water mixture, an oil-water-air mixture, or grease mixtures are used as lubricants. To improve the lubricating and cooling effect, the combined use of supercooling of the strip and roll surface and roll lubrication on the run-in side of the rolling stand is proposed, in which the two media—water and lubricant—are supplied separately to the rolls and the rolling stock and are applied to different points of application on the surface of the roll. Separate supply lines to the spray bars are provided for water and the lubricant.